Microwave energy indicator

Abstract

An irreversible label or indicator of whether a surface or object has received microwave exposure and to delineate microwave heating or oven heating. Because microwave cooking has become an ubiquitous method for food preparation, and that energy and power in a microwave oven can vary from one unit to another, and within the spatial volume of the appliance, it is desirable to have a dynamic indicator that can provide an effective indicator of microwave exposure under such conditions.

What is claimed is: 
     
         1 . A microwave radiation indicator, comprising
 a transparent polyester film having a thickness of about 0.003″ to 0.005″, to a portion of which a conductive carbon area is applied;   a coating of irreversibly thermochromic material, on the polyester film;   wherein exposure to microwave energy causes the temperature of the conductive carbon to rise to at least the irreversible thermochromic transition temperature of the thermochromic material.